Tobacco use remains a major cause of premature death in the United States, with 30% of cancer deaths and 18% of all deaths directly attributable to smoking. Initiation of tobacco use occurs primarily during adolescence, with smoking rates peaking in young adults. Although tobacco smoke contains over 8000 constituents, most animal models used for testing smoking cessation therapies focus on the effects of nicotine alone in adult males. This lack of attention to both the non-nicotine constituents of tobacco and the age of first use may account for the low success rate of current tobacco cessation medications. With clinical data showing sex differences in tobacco dependence, it is also important to study females. Our group has been one of the only ones to examine the impact of non-nicotine constituents on nicotine actions in both adolescents and adults. We have shown that adult and adolescent rats will self-administer cigarette smoke extract (CSE), made by bubbling cigarette smoke through saline solution. CSE is more reinforcing in adult male rats than equivalent doses of nicotine alone, and animals that self-administered CSE are more sensitive to both stress- and nicotine-induced reinstatement of drug-seeking behavior than animals that worked for nicotine alone. Our data also suggest that both adolescents and adults exhibit more somatic withdrawal upon cessation of chronic CSE administration than nicotine. These findings indicate the importance of assessing the effects of nicotine in the presence of other tobacco smoke constituents. The objective of the current application is to examine mechanisms underlying enhanced withdrawal and drug-seeking behavior in animals that have been chronically treated with CSE. In addition to evaluating adolescent and adult males, we will initiate one of the first studies of the impact of CSE exposure in females. The specific aims of the proposal include: 1) Comparison of somatic and affective withdrawal symptoms following chronic nicotine and CSE exposure in adolescent and adult rats of both sexes. We will further test the hypotheses that monoamine oxidase inhibition, enhanced nicotinic acetylcholine and/or kappa opioid receptor function underlie the increased somatic withdrawal that we have observed following cessation of chronic CSE treatment in adult and adolescent males; 2) Comparison of stress-induced reinstatement of nicotine- and CSE-seeking behavior in adolescent and adult males, and assessment of the role of a34 nicotinic receptors in mediating drug craving; 3) Establish a dose-response relationship for acquisition of self-administration of CSE, and equivalent doses of nicotine alone, in females. The approach is innovative in that it aims to bridge the gap between human and animal studies by examining the combined impact of tobacco smoke aqueous components. The proposed research is significant in that it provides an initial step towards a more comprehensive approach to determining neural mechanisms underlying tobacco dependence, and may result in the development of improved clinical therapies for smoking cessation.